Keep only the most complete data

src/Models/Journal.php

@@ -21,6 +21,9 @@ public function add(array $journal): array
     {
         foreach ($journal as $key => $value) {
             if ($this->shouldKeepAttribute($key, $value)) {
+                if (is_array($value)) {
+                    $value = array_unique($value);
+                }
                 $this->list[$key] = $value;
             }
         }

src/Models/Model.php

@@ -80,7 +80,7 @@ protected function shouldKeepAttribute(string $key, $value): bool
             return true;
         }
 
-        return $function($this->list[$key]) > $function($value);
+        return $function($this->list[$key]) < $function($value);
     }
 
     /**

tests/Integration/RegressionTest.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace PubPeerFoundation\PublicationDataExtractor\Test\Integration;
+
+use PubPeerFoundation\PublicationDataExtractor\Fetcher;
+use PubPeerFoundation\PublicationDataExtractor\Test\TestCase;
+use PubPeerFoundation\PublicationDataExtractor\IdentifierResolver;
+
+class RegressionTest extends TestCase
+{
+    /** @test */
+    public function it_can_extract_issns()
+    {
+        $identifier = new IdentifierResolver('10.1002/0471142727.mb0418s103');
+        $dataFetcher = new Fetcher($identifier->handle());
+
+        $output = $dataFetcher->fetch();
+
+        $this->assertArrayIsValid($output->getData());
+
+        $issnIdentifiers = array_filter($output->getData()['identifiers'], function ($identifier) {
+            return 'issn' === $identifier['type'];
+        });
+
+        $this->assertCount(1, $issnIdentifiers);
+        $this->assertTrue('John Wiley & Sons, Inc.' === $output->getData()['journal']['publisher']);
+        $this->assertCount(1, $output->getData()['journal']['issn']);
+    }
+}